We present a new class of micropatterning techniques that incorporates
a surface energy gradient on a single substrate. By combining microcontact
printing and vapor deposition methods, this technique provides fast, reproducible,
and high-quality micro-scale gradient patterns on silicon substrates.

For creating chemical patterns, elastomeric stamps with an array of
stripes 1-25 m m wide are used to create a stationary
contact with a silicon substrate. This substrate is then immersed in a
chlorosilane vapor for 1 hour. Organosilane molecules in a vapor phase
react with OH groups on areas of substrate not covered by the elastomer
stamp, resulting in the formation of a patterned organosilane self-assembled
monolayers (SAMs). The substrate is then exposed to a gradient of UV-ozone
radiation, which gradually changes the hydrophobic SAMs layer to hydrophilic
species. The resulting gradient shows a range of contact angles from 25-95°
.

These gradient energy substrates with chemical patterns are developed
to (1) serve the development and calibration of next generation SPM techniques
and (2) generate libraries for combinatorial studies of thin film phenomenology,
where a systematic variation of interfacial surface energy is significant
parameter along one axis. The graded oxidation process presents a systematic
variation of surface chemical composition. We have utilized contact angle
measurements and Atomic Force Microscopy (AFM) to investigate the influence
of the chemical gradient and pattern size on the morphology of ultrathin
dewetting polystyrene films. We show that the dewetting patterns are correlated
to the surface energies and pattern period leading to the formation of
droplet arrays.